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Pros of incest outweigh cons for mongooses

If you find yourself looking around the table over the holiday and thinking, “I can’t believe I’m related to these people,” just be glad you’re not a mongoose. If you were, you might be thinking, “I can’t believe I’ve mated with all of these people.” For the cat-sized mammals, native to central and east Africa, it’s safer to have sex with a close relative than risk death by venturing out into the world to find a mate, according to a study published online today in Biology Letters. Newly formed mongoose groups have a mortality rate three times higher than that of established ones, and mongooses that encroach on neighboring groups are often met with violence. Perhaps consequently, an analysis of 14 packs of mongooses in Uganda’s Queen Elizabeth National Park finds that inbreeding is the norm: 63.6% of the pups were conceived between two members of the same natal group, the social group into which an individual is born. Twenty-seven percent of offspring were conceived by mothers that bred within their natal group and were related to their mates by a coefficient of relationship of 0.25 or higher—the equivalent genetic similarity between half siblings or a grandparent/grandchild. Additionally, 7.5% of pups were conceived by parents related by 0.5 or more—full siblings or a parent/child. Father/daughter incest occurred eight times during the study, but interestingly, mother/son breeding was not observed—perhaps due to the fact that males take longer to reach sexual maturity and their mothers are dead by the time they’re ready to mate. Researchers speculate that, at least for mongooses, the genetic problems caused by inbreeding are perceived to be less dangerous than leaving the pack in search of new mates.